Overhead cam valve lifter



970 E. w. SCHEIBE ET AL 3,509,858

OVERHEAD CAM VALVE LIFTER Filed May 20, 1968 IN VEN TOR BY &dwarc2 Ore?? A 7' TORNEY United States Patent O 3,509,858 OVERHEAD CAM VALVE LIFTER Elias W. Scheibe and Edward Orent, Grand Rapids, Mich., assignors to General Motors Corporation, Detroit, Micln, a corporation of Delaware Filed May 20, 1968, Ser. No. 730,486 Int. Cl. F011 1/04 U.S. Cl. 123-90 1 Claim ABSTRACT OF THE DISCLOSURE An overhead valve and cam engine having a pressurefed hydraulic valve lifter interposed directly between the valve and cam, with the lifter pressure chamber being formed between an upright cup resting on the valve stem and a plunger abutting the bottom wall of a larger inverted cup which engages the cam and is slidably guided in a fixed bore surrounding the valve stem.

BACKGROUND OF THE INVENTION The invention relates to hydraulic lifters or tappets such as are used, for example, in maintaining substantially zero lash in the valve operating mechanisms of internal combustion engines, and particularly to improvements in the application of such devices directly between an overhead cam and the valve stem actuated thereby.

While the prior U.S. Pat. No. 2,175,467 to Johnson shows it broadly old to interpose a hydraulic valve lifter directly between a cam and a valve directly below it, the engine is of the inverted L-head type rather than the overhead cam and valve type and the number of parts involved and lack of compactness would render the lifter too costly and large for use in modern relatively lowheight overhead cam engines. Also, the plunger in that lifter is slidably fitted to the cam driven outer member, which precludes manufacture and installation of all closetolerance parts as a sub-assembly for use in various cam driven follower members. British Pat. No. 538,952 shows a hydraulic lifter between a cam and its driven end of the valve rocker wherein the plunger and its slidably fitted cylinder member are insertable as a sub-assembly in the rocker, and is thus distinguishable from applicants invention which eliminates the use of a rocker and has the valve stem, rather than the cam, drivingly engaging the plunger cylinder member.

SUMMARY OF THE INVENTION My invention not only eliminates the usual valve rocker in an overhead cam engine by interposing the hydraulic lifter directly between the cam and valve stem, but arranges the relatively slidable and close-tolerance fitted plunger and cylinder member within a direct cam-driven follower member which is slidably guidable in a fixed bore of the engine. All side thrust on the close-fitting surfaces of the plunger and its hydraulic cylinder member is accordingly avoided, with consequent reduction in wear rate of those surfaces which is the principal terminating factor in the life of such parts. Also, extreme compactness is achieved by use of cup-shaped outer and inner members for the cam follower and plunger cylinder, with the plunger arranged to abut the closed end of the inverted cup-shaped follower or outer cylinder member. Further, the plunger and its cup-shaped cylinder, together with the check valve, plunger spring and check valve retainer can be manufactured as a standard-size sub-assembly for use with difierent outer cylinder members to accommodate various engines.

BRIEF DESCRIPTION OF THE DRAWING FIG. 1 is a transverse sectional view through the upper portion of an internal combustion engine incorporating a hydraulic valve lifter arranged according to the invention.

FIG. 2 is an enlarged fragmentary sectional view taken substantially along the lines 22 of FIG. 1.

FIG. '3 is an exploded view of the internal parts of the lifter, shown in perspective.

DESCRIPTION OF THE PREFERRED EMBODIMENT Referring now in detail to the drawing and first to FIG. 1, an engine cylinder block 1 is shown, with a cylinder 2 in which an engine piston 3 operates in usual manner. Covering the upper end of the cylinder is a cylinder head 4 in which a poppet valve 5 is slidably fitted to control opening and closing of the port 6 communicating with the combustion chamber 7 above the piston. The valve is biased to its normally closed position shown, by a coil spring 8. Downward actuation of the valve in the opening direction is effected by a cam 9 on a camshaft 10 which directly overlies the upper end of the valve stem 11 and is suitably journaled in a housing 12 bolted to the cylinder head.

In accordance with the invention, a hydraulic valve lifter designated generally by the numeral 13 is interposed directly between the cam and the valve stem. Hydraulic fluid in the form of oil from the engine lubricating system is supplied under moderate pressure (10 to 50 lbs. per square inch) via an oil gallery 14 and branch port 15 to the valve lifter.

Referring to FIG. 2, which illustrates a preferred embodiment of the lifter construction, and to FIG. 3 which more clearly shows certain of the parts, it will be seen that the lifter comprises an inner, upwardly presenting cup-shaped cylinder member 16 whose closed end 17 rests on the upper end of the valve stem 11. Surrounding this inner cylinder member is an inverted cup-shaped outer cylinder member 18 whose closed upper end 19 is in abutting engagement with the cam 9. A plunger 20 has a close sliding fit for reciprocation within the cylinder member 16, and is normally biased upwardly therein by a plunger spring 21 so that its upper end 22 normally abuts the closed end 19 of the outer cylinder member. The spring 21 reacts against the closed end 17 of the inner member to maintain it in abutment with the valve stem. A fluid pressure chamber 23 is thereby formed within the inner cylinder member below the plunger, and this chamber is supplied with engine oil from the gallery 14 and housing port 15 via a communicating side port 24 in the outer cylinder member and an axial port 25 in the plunger. Controlling this plunger port for one-way flow inwardly to the pressure chamber 23 is a check valve shown in the form of a ball 26 which closes against the seat 27 on the plunger in response to pressure in the chamber 23 exceeding the aforementioned supply pressure. A check valve retainer or cage 28 limits opening travel of the ball 26 to the amount necessary to accommodate replenishment of the chamber 23 with oil which normally escapes therefrom between the sliding surfaces of the plunger and cylinder member 16 as leak-down during cam induced opening movements of the engine valve 5. As shown, the valve retainer cage is held in position against the plunger by the plunger return spring 21.

During each engine valve opening or lift stroke of the cam 9, downward movement of the outer cylinder member 18 tends to force the plunger further into the inner cylinder member 16, and the resulting pressure rise in the chamber 23 causes the check valve ball 26 to seat itself. With continued downward movement the inner cylinder member is likewise moved downwardly under the thrust of the trapped oil in the chamber 23, forcing the engine valve to open against its spring 8. On the return stroke to the base circle portion of the cam 9-1mder the biasing force of the engine valve spring 8 the oil pressure in the lift chamber 23 is relieved and the plunger spring 21 tends to expel the plunger upwardly in the inner cylinder member 16 to maintain abutment between the plunger and the outer cylinder member end 19, while maintaining the inner cylinder member 16 in abutment 'with the valve stem. Such relative movement of the plunger and inner cylinder and release of pressure in the chamber 23 allows the check valve 26 to move oif its seat for flow of replenishment oil to the chamber 23 as necessary to completely fill it preparatory to the lift operating cycle.

Some intermittent separating movement between the plunger and the closed end 19 of the outer cylinder member nevertheless occurs, during engine operation, particularly at high speed, such that oil entering the outer cylinder member via the port 24 is enabled to reach the plunger port 25. To facilitate and insure such communication at all speeds however, the plunger side walls 29 define a fluid reservoir chamber 30 within their upper ends which is in constant direct communication at all times with the plunger port 25, and the upper extremities of these walls are partially cut away at one or more places to form notches 31. Thus, the oil flowing into the outer cylinder member through the port 24 is free at all times to enter the plunger reservoir 30 so that it is kept reasonably full for passage through the plunger port 25 when the check valve is unseated.

The outer cylinder member is laterally guided by having a sliding fit in the bore 32 provided therefor in the housing 12 concentric with the valve stem. Such lateral support for the outer cylinder member relieves the lifter plunger and inner cylinder member 16 of all side thrust as would otherwise be induced from the cam. As a result, the closetolerance fit of their mutually sliding surfaces is less subject to wear, and the operating life of the lifter is accordingly greatly prolonged. Centering of the inner cylinder member on the valve is effected to some extent by centrally undercutting, as at 33, the bottom of the closed end 17 to socketably receive the upper end of the valve stem. Various means may also be provided for additionally cen tering the inner cylinder member, as well as blocking drainage of oil downwardly around the inner member 16 from within the upper portion of the outer cylinder member where such oil would excessively lubricate the valve stem 11 and possibly be drawn into the engine combustion chamber 7. Such means might take the form of a resilient diaphragm or sheet metal stamping slidably bridging the annular distance between the inner and outer cylinder members 16 and 18, but in the arrangement shown is provided by forming the inner wall of the outer member with a land 34 to slidably engage the outer periphery of the inner cylinder member 16.

It will be appreciated that the inner cylinder member 16 and its enclosed plunger 19, check valve 26, retainer cage 28 and plunger return spring 21 may be manufactured as a sub-assembly for insertion and removal from the outer cylinder member 18 as engine servicing may require. This is of considerable advantage since the closetolerance fit between the sliding surfaces of the plunger and inner cylinder member need not be disturbed on such occasions, and reinstallation of such sub-assembly need not be restricted to the particular outer cylinder member 19 in which it was formerly associated. Also, such subassemblies may be manufactured to a standard size and its accommodation to outer cylinder members of various sizes for different engines may be provided for by merely maintaining the same internal diameter of the outer member land 34.

We claim:

1. In an overhead valve and camshaft engine having a generally upwardly extending valve stem and a lifter guide bore concentric with the valve stem, a cam spaced above the valve stem and a hydraulic valve lifter interposed between the stem and cam; said lifter comprising an outer cup-shaped member including a head closing its upper end and an inner cup-shaped member in oppositely presenting relation with the closed end of the inner member abutting the stem and the closed upper end of the outer member abutting the cam with said outer cup-shaped member being slidably reciprocable in said bore; said head having a lower central bore and a smaller concentric bore above the lower bore, a plunger slidably reciprocable in the inner member and extending therefrom into diect abutting engagement with the underside of said closed end of the outer member; a spring interposed between the plunger and the inner member for maintaining said inner member closed end abutting the valve stem and said outer member closed end abutting the cam; said plunger having a notched upper end urged by said spring into abutment with an upper end 'wall of said smaller bore; and means for supplying and maintaining a body of hydraulic fluid in thrust transmitting relation between the closed end of the inner member and the plunger; said means including a side port in the outer member, a communicating axial port in the plunger and a check valve controlling said plunger port for one way flow of said fluid inwardly of the inner member.

References Cited UNITED STATES PATENTS 2,870,757 1/1959 Dayton. 2,938,508 5/ 1960 Pa-penguth. 3,286,702 11/1966 Dadd.

BENJAMIN W. WYCHE III, Primary Examiner US. Cl. X.R. l23-l93 

